The present invention relates to communications networks including mobile asynchronous transfer mode (ATM) and Internet-Protocol (IP) networks. More particularly, the invention relates to route optimization and location management in communication networks.
The term xe2x80x9ccalling party""s switch,xe2x80x9d as used herein, is the network node from which a call originates, i.e., a call is generated from one of the endpoints of the calling party""s switch, or a network node along the path of the call that is enabled to perform route optimization or is mobility-enhanced.
The term xe2x80x9chome switch,xe2x80x9d as used herein, is the switch to which an endpoint is assumed to be connected in the default mode. The address of the endpoint is derived from the network address of its home switch.
The term xe2x80x9cvisiting switchxe2x80x9d as used herein, is the switch at which an endpoint is currently located.
The term xe2x80x9clocal switch,xe2x80x9d as used herein, is an intermediate node between the calling party""s switch and the home switch to which a call is cranked back during call setup before continuing on to the visiting switch.
The term xe2x80x9cnetwork node,xe2x80x9d as used herein, is a system in a communications network that performs a switching or routing functions. A network node can be an access node if it has links to endpoints (users). A network node can be a transit node if all its links are to other network nodes with no links to endpoints. Examples of network nodes are ATM switches, IP routers, SONET cross-connects, telephony switches, WDM (Wavelength Division Multiplexed) optical cross-connects and other similar systems.
In a mobile network, the term xe2x80x9cnetwork node,xe2x80x9d refers to an access point or a base station (which may include an ATM switch).
The term xe2x80x9cmobile user,xe2x80x9d as used herein, refers to a person connected to (or who will be connecting to) a node that is not a mobile user""s home switch. A mobile user doesn""t necessarily need a wireless interface.
The term xe2x80x9ccall,xe2x80x9d as used herein, refers to any connection (e.g., voice, data, etc.) between an originating party and a receiving party over a communication path.
The term xe2x80x9ccall-forwarding,xe2x80x9d as used herein, refers to a method in which a connection set up is continued from the home switch to the visiting switch of a called user.
The term xe2x80x9ccommunication path,xe2x80x9d as used herein, refers to the path from the originating party to the receiving party over the network.
The term xe2x80x9ccrankback,xe2x80x9d as used herein, refers to a backtracking of the connection setup procedure (partial release of reserved resources).
The use of ATM and IP technology in mobile communication networks is becoming increasingly common. In mobile ATM networks, xe2x80x9chandoff proceduresxe2x80x9d and xe2x80x9clocation management proceduresxe2x80x9d are needed to support user mobility.
Location management is the process of tracking mobile users and locating them for delivering yet-to-be-established incoming call to the mobile user. In the process of conducting location management, the paths proposed for establishing the connections can become xe2x80x9csub-optimal,xe2x80x9d i.e., the paths to be used may not be the best paths between the two endpoints of the connections.
Mobile user tracking procedures update the home node of a mobile user with information about the location of the mobile user. This information is used to deliver incoming calls to mobile users at their current location.
One prior art location management method is called xe2x80x9ccomplete releasexe2x80x9d and is described with reference to FIG. 1A. By this method, a mobile user 110 has a home switch 116, but mobile user 110 is located near a visiting switch 118. A calling party 114 attempting to call mobile user 110 will have the call routed to home switch 116 along connection 112. Location information will be transferred back to the calling party 114 xe2x80x9cadvisingxe2x80x9d calling party 114 that the mobile can be reached via visiting switch 118, whereupon connection 112 will be completely dropped, and connection 120 will be established to connect the call.
In the method illustrated in FIG. 1A, since the entire connection is being rerouted (i.e., there is no common path between the first connection 112 and the second connection 120), latency is an issue. Considerable time and network resources are spent establishing the new connection 120 over an entirely new path, while dropping the first connection 112.
Another prior art location management method, xe2x80x9ccall forwarding,xe2x80x9d is illustrated with reference to FIG. 1B, by which a call is forwarded from the home switch of the mobile user to the visiting switch of the mobile user. Referring to FIG. 1B, the path between calling switch 114 and the visiting switch 118 is established by simply extending a new path 122 (shown in dotted line) to the visiting switch 118 from the old network node 116, in a xe2x80x9cconnect-the-dotsxe2x80x9d fashion. Using this method, lower call setup latencies can be achieved because the old and new base stations are simply interconnected as needed. However, the path taken by the connection will often be sub-optimal, because the new path added on to the old one may follow a circuitous route.
Another prior art scheme, called a two-phase crankback scheme, allows for the call setup procedure to be cranked back from the home switch to a local network node, and then rerouted. This crankback is executed at a local level, which means that the overall end-to-end path taken by the connection could still be sub-optimal.
None of the prior art location management methods determine whether the route established between the originating point and the network node closest to the mobile user is optimal, nor do they optimize the connection path to establish such an optimal route. Suboptimality that is introduced during connection setup is primarily due to lack of exact information about the location of the mobile user at the call originating switch, and suboptimality occurs after connection setup because of movements by communicating mobile user. These suboptimal paths result in an inefficient usage of network resources.
Thus, there exists a need for a location management system which provides an efficient location management scheme/method to optimize routes of connections such that an efficient usage of network sources results.
Two location management schemes are disclosed herein. In a first embodiment, a procedure for finding an optimal path between a calling switch and a visiting switch node is integrated in the call set up procedure. The connection set up procedure starts by setting up a connection path between the calling switch and the home switch. Then, an xe2x80x9coptimal crossover nodexe2x80x9d is determined along the connection path and then the connection path is cranked back starting from the home switch and moving towards the optimal crossover node. Once the optimal crossover node is reached, the a connection set-up proceeds to set up a connection between the optimal crossover node and the visiting switch.
In an alternative embodiment, first a connection is set up between the calling switch and the home switch. Then the connection is extended to the visiting switch either by the call-forwarding or by two-phase crankback method. This results in a quickly routed, but sub-optimal connection. Once the connection extension is completed by call forwarding or by the two phase crankback scheme, the route is optimized by selecting a segment on the sub-optimal connection for route optimization and then utilizing the method of the first embodiment to establish an optimally routed connection.
The method of determining an optimal connection path and rerouting the existing connection path to this optimal connection path, as described in the first embodiment, is applicable to all communication networks deploying connection-oriented technologies. These communications networks include land-line networks and mobile networks. Similarly, the method of route optimization for optimizing a suboptimal connection, as described in the second embodiment, is applicable to all communication networks deploying connection-oriented technologies. These communications networks include land-line networks and mobile networks.
Within communications networks, the kinds of networks to which the present invention is applicable includes flat networks, hierarchical networks, and PNNI-hierarchical networks.